1. Field of the Invention
The present invention relates to an image scaling processing device and an image processing method of digital data such as facsimile, scanner, digital copy, or the like and more specially, to an image scaling processing device and an image processing method enlarging or reducing an image including half-tone shades at any scale factor.
2. Description of the Related Art
In the previously known image scaling processing device and the image processing method having enlargement and reduction function for this kind of a binary-valued image, a thinning processing is made at intervals corresponding to a reduction ratio at the time of reduction and, at the time of enlargement, after enlarging by integral times, the thinning processing is made at periodic times corresponding to a scale factor and thus enlargement and reduction processing is performed. The technology of this kind is described in Japanese Patent Application Laid-Open No. 164896/1994 and Japanese Patent Application Laid-Open No. 253140/1994.
However, according to a constitution of the above described art, the thinning processing is periodically made regardless of an input image data. For this reason, irregularity of a character outline part in a character portion of the input image becomes conspicuous and a noise is increased at half-tone data, thereby reproductivity is lost. Again, a lot of memory is required for keeping the data after the image processing is made as large as scale factor is enlarged.
The present invention is made in view of the above described subject and it is the object of the present invention to offer the image scaling processing device, wherein a binary-valued image can be given a enlarging and reducing processing at optional scale factor with the minimum scale of a circuit constitution and the character portion is smoothed when enlarged and a black line is kept when reduced. Further, a noise is not generated in the half-tone portion according to values of enlargement or reduction ratio, thereby reproductivity of gradation in the half-tone is maintained.